Why not just kill the coastal before putting something else down?

It's a hayfield, I fear it would just over run it from the edges.

My "yard" that I'm carving out is in the middle of a 45 acre field,

Yard is going to be fenced at about 60x60

TIF would get overrun if you don't do anything to kill it first. And I would be concerned, as you are, that the coastal would come in from the sides.

You might be successful with St Augustine. For a dollar you could try a patch of it under a tree or in some other shady spots (north side of a building). Mow the St Augustine at the mower's highest setting and see if it doesn't overrun the coastal. St Aug will overrun all the other bermudas, but coastal is not usually in the mix of turfgrasses. St Augustine will grow out 15 feet per year in all directions once it is established. The first year's extensions will be sparse but that will fill in and get dense the second year. And it will push out another 15 feet the second year. So if it overruns the coastal, then it will work for you. I'm doing this right now with a house I bought in 2014. The yard was all weeds except for narrow strips of St Augustine in the shady parts near the house. Now it is dense St Aug out about 30 feet and still going.

Direct sun, no shade, so st augustine is out. Looks like my best bet will be to level this and slowly drop my mower settings. Solid clay, so I will add sand for leveling.

Appreciate your help dchall, I didn't think I would have many options here, lol

Where do you live? Are there clay factories nearby, because almost nobody lives on solid clay. Do this test: Get a straight sided jar, fill it half way with soil, place a ruler next to the jar and take a picture showing the height of the soil. Then fill the jar with water and a small squirt of any liquid soap. Shake that up to break up any clods and put it down. After 2 minutes take another picture with the ruler. After 2 hours take another picture with the ruler. After 2 days take another picture with the ruler. The stuff that settles in 2 minutes is sand. The stuff that settles on top of the sand in 2 hours is loam. The stuff that never settles after 2 days is clay. If you can see through the water on top after 2 days, you have almost no clay. You can still have hard soil with no clay, but you don't want to treat for clay if you don't have any clay. Do the jar test and either report back here or post the pictures here. I'm guessing you'll have 75% sand at the least and no clay at all.

St Augustine (Floratam variety) LOVES full sun with no shade. You'll need a more powerful lawnmower than I have, though. I have to make half cuts to get through it.

When we were preparing for construction, we had probably 10 test holes dug.

They were all between 5 and 6 ft. Aside from the top inch or so, It was Black clay down to about 4 ft, then yellow clay.

I am intrigued by your mention of Floratam, but my reservations are for water usage.

All St. Augustine varieties I have had used 2-3 times as much water as most Bermudas. Shoot, it's Almost December and we haven't had any significant rain in weeks... maybe early october?

Where do you live?

You might be an expert at diagnosing soils, but 99% of the people who come here claiming to have clay find that the jar test disagrees. Most have very little, if any, clay at all. More likely they have a mix of minerals and salts that mimic clay. If you want to fix the soil, you really need to know if you have clay issues or salt issues. The fix for each one is very different. Once you discover that you have no clay, then a soil test will tell you about the salts. But I would

You said, All St. Augustine varieties I have had used 2-3 times as much water as most Bermudas.

Then you were watering incorrectly. When you are doing it right, then all grasses need about the same amount and frequency of water if you want them to look healthy. A friend of mine in Phoenix waters his St Augustine 2x per week when the temps get above 100 degrees and 3x per week above 110. The difference between bermuda and St Augustine is that if you want to conserve water, then you can stop watering bermuda and expect it to return after months of no watering. If you stop watering St Augustine in the hottest heat of summer and let it go for 2-3 months, then it will likely die out making room for weeds and bermuda.

I live in Bandera and have only watered the St Augustine maybe 6 times this year. The water has not been on since August. Recently we got some very low humidity weeks, so I'm going to water it again tonight. The grass itself does not look like it needs water, but the soil is dry as a bone down deep. So I'm watering to help the soil microbes. As for rainfall we got 1/4 inch this month, 1.5 inches in October, and 4 inches in Sept. Here's a picture of the front showing how far the St Aug has moved. When I bought in 2014 the only St Augustine was 4 inches out from the edge of the walkway.

Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.

And again, where do you live?

And also, I'm not a soil expert.

Just repeating what the septic and foundation guys said...

My first response must not have posted.

I am between Temple and Waco. 1/2 an hour of light rain turns everything into a slip and slide...

Slip and slide is a symptom of too much magnesium salts in the soil. Then it turns rock hard when it dries.

Do the jar test and send a soil sample to someplace (not TAMU) to get the salts (calcium, magnesium, potassium, and sodium) tested. Or...just assume you don't have any clay and see if the grass grows. If the grass grows, then that's all you really care about. Don't ever put magnesium (Epsom salts) or calcium on the soil unless and until you have a soil test that calls for those additions.

Never heard that, very interesting, thanks.

I would probably do the jar test this weekend.

The Grass Grows fine, like I said this is in the middle of a big hay field

Where would I send it for testing, any suggestions?

My suggestion is to get the Logan Labs $25 test and go to a different website for interpretation. Search for "posting a soil test for interpretation". Why go to a different site for interpretation? Because the good folks at this site quibbled so much about the Logan Labs test that the guy who used to do the LL interpretation here left the site. The quibbles started with a difference between pH (offered by LL) and buffer pH (offered elsewhere). Things deteriorated from there. In your case, being in Central Texas, the last thing you need to deal with is pH and buffer pH. You live on miles of limestone, so your soil has a pH of 8 and there's nothing you can do about it. You should be more interested in the soil salts and how to correct those. Without the benefit of a Logan Labs test interpreter we have a couple people here who will read most any test for you except a Logan Labs test. From what I've seen the interpretations are a little more haphazard in that they don't discuss every number on the test. That leaves me feeling like they might have missed something important. To me I want to know if the overlooked items are or are not important, so my recommendation to post the results here is lukewarm at the very highest.

Logan Labs was picked by a group of lawn gurus after reviewing test methods and sending samples over and over to different labs. Logan Labs and UMASS were selected to be a distant first and second place far and above the rest of the pack. The reasons for picking those two was repeatibility (ability to get the same results from the same soil sample tested at different times) and the ability to agree with each other time after time. They also provide quantitative results and not just red-yellow-green stoplight indicators of which nutrients are bad or good. The quantitative results are needed for interpretation because the results will be different if you sample the soil at 4 inches one time and 6 inches for another test.

Soil tests are not rocket science, but they are interactive chemistry. Adding too much of one chemical can affect how the soil interacts with others. For example a low pH soil has plenty of available iron, but if you overdose it with calcium, the iron will bind with the calcium making it unavailable to the grass. Our calcitic Texas soil already has so much calcium that getting any iron out of it at all is a headache.

So that was way more information than you asked for. Texas A&M soil tests have been suspect for decades. In the early 2000s they issued an apology for doing their tests wrong.

Wow. Thanks for the input.

Being a complete rookie in this, I do appreciate it.

I am interested to see what this test will show. This being what I guess would be considered "Blackland prairie" all the farmers just call it clay. I was also surprised about the tamu thing, as most consider them the end all be all...

I did get a chuckle out of the story of the LL guy... the internet is full of self-appointed experts that will pick strange hills to die on...

You're in prime Bermuda territory, but you'll probably get some infiltration from the older Bermuda no matter what you do. If you can live with 90% perfection, just start sodding in a good quality hybrid...cant hurt

Edit, it will definitely grow on the high magnesium super tight quasi clay you have. Bermuda is extremely tolerant of poor soil